Vehicle warning signal switching apparatus including circuit momentarily interrupted only in response to movement in one or an opposed pair of directions

ABSTRACT

A vehicle warning-signal arrangement, particularly useful for the selective disabling and self-restoration of automatic sequential light flashings aboard school buses, involves a dooractuated multi-circuit electrical switch, one circuit of which is momentarily interrupted in but the door-closing half of a switching cycle, together with an operator-latched solenoid switch and an automatic flasher, the switch interconnections allowing warning lights to be turned on by the operator and stop lights to be turned on automatically when a door is then opened, but also insuring that door closure will in turn restore a circuit condition permitting a door-opening without attendant improper flashing of the stop lights; the multi-circuit switch is operated by a plunger which momentarily disconnects one set of contacts only during its inward or door-closing travel as the result of unique coaction between a shaped enlargement on the plunger, an elastomeric O-ring closely surrounding and rideable over the enlargement of the plunger, and an apertured springbiased pole-carrying plate through which the plunger but not the O-ring will pass.

United States Patent 1191 Parolin 1 Aug. 26, 1975 1 1 VEHICLE WARNINGSIGNAL SWITCHING APPARATUS INCLUDING CIRCUIT MOMENTARILY INTERRUPTEDONLY IN RESPONSE TO MOVEMENT IN ONE OR AN OPPOSED PAIR OF DIRECTIONS[75] Inventor: John J. Parolin, Boston, Mass.

[73] Assignee: Cole-Hersee Company, South Boston, Mass.

22 Filed: Feb. 26, 1973 21 Appl. No.: 335,779

Primary Examiner-Marshall M. Curtis Attorney, Agent, or Firm-CharlesHieken; Jerry Cohen AMBER SCHOOL BUS l 5 7 ABSTRACT A vehiclewarning-signal arrangement, particularly useful for the selectivedisabling and self-restoration of automatic sequential light flashingsaboard school buses, involves a door-actuated multi-circuit electricalswitch, one circuit of which is momentarily interrupted in but thedoor-closing half of a switching cycle, together with anoperator-latched solenoid switch and an automatic flasher, the switchinterconnections allowing warning lights to be turned on by the operatorand stop lights to be turned on automatically when a door is thenopened, but also insuring that door closure will in turn restore acircuit condition permitting a door-opening without attendant improperflashing of the stop lights; the multi-circuit switch is operated by aplunger which momentarily disconnects one set of contacts only duringits inward or door-closing travel as the result of unique coactionbetween a shaped enlargement on the plunger, an elastomeric O-ringclosely surrounding and rideable over the enlargement of the plunger,and an apertured springbiased polecarrying plate through which theplunger but not the O-ring will pass.

7 Claims, 7 Drawing Figures AMBER RED RED STOP LIGHT mmmmszsms 3802,1593

SHEET 1 [IF 3 AMBER 7 RED RED STOP LIGHT SCHOOL BUS l\ ls FLASHER 2dPATENTEU wrsz m 3 902,159

III a l VEHICLE WARNING SIGNAL SWITCHING APPARATUS INCLUDING CIRCUIT IMOMENTARILY INTERRUPTED ONLY IN RESPONSE TO MOVEMENT IN ONE OR ANOPPOSED PAIR OF DIRECTIONS BACKGROUND OF THE INVENTION The presentinvention relates to improvements in electrical switching apparatus suchas is used in controlling Warning lights aboard school buses and thelike, and, in one particular aspect, to novel and improved switchingarrangements for operator-selected control over certain automaticdoor-actuated excitations of warning lights, as well as to uniquemomentaryinterrupting switch constructions which are especially suitedto the requirements of such switching arrangement's.

A conventional attention-commanding safety warning-light system forschool buses involves the flashing of amber warning lights as thevehicle approaches a stop, and then the flashing of red stop lights solong as the door or doors are open to permit the boarding or dischargeof passengers. Preferably, such a system is under control ofadoor-operated switch which will insure that the stop lights mustoperate without fail during' those hazardous times when passengers maybe alighting or entering. However, it is also mandatory that the samevehicle not display flashing stop lights when at rest for otherpurposes, such as a temporary halt with door open as required by law ata railroad crossing. These conflicting requirements can be satisfied inpart by way of a simple type of operatoractuated switching which-woulddisable the warning system, but this introduces another control anddevice to which an already busy operator must give attention, and thereis no assurance that thewarning system will always be reset to functionwhen needed. More complex networks, involving additional door-operatedswitches, for example, tend to introduce significantly higher costs,both as to system components and installation.

According to the invention, there is warning signal means, such asflashing warning lights on a school bus, responsive to energization withelectrical energy for providing a warning signal. First manuallyactuated switching means, such asa relay with a holding winding andcontacts delivers electrical energy to the warning signal means when inthe closed condition, such as when the contacts are closed, has holdingmeans, such as the holding winding, responsive to interruption of aholding energy for returning the first switching means to the opencondition, such as when the contacts are open, and is responsive to'manual actuation for assuming the closed condition. There is a sourceof the holding energy. Second switching means has an armature movable infirst and second opposed directions and includes means responsive tomovement of the armature in the first direction for coupling the holdingenergy to the holding means and means responsive to movement of thearmature in the second direction for interrupting the coupling of theholding energy to the holding means to thereby restore the firstswitching means to the open condition.

In accordance with certain aspects of the present teachings, thecreation of a relatively simple and inex pensive warning-light systemfor school buses, involving only a single door-operated switch unit,which will reliably condition itself for single-cycle automaticsequencing of'both flashing warning and stop lights upon actuation bythe operator, is linked to the concept of having the door switchmomentarily interrupt one of its switching circuits only when the dooris being closed after having been opened. That momentary interruption iseffective to reset a self-holding solenoid switch by which the operatorhad initiated one cycle of sequencing of the flashing lights, and,thereafter, the operator may intentionally omit the sequencing byrefraining from actuation of the solenoid switch when the bus is to stopfor some purpose other than admitting or discharging passengers. Oncethe system has been operator-conditioned to follow the desiredsequencing, however, it will be strictly observed in accordance withdoor opening and closure, without further operator attention.

The momentary-interrupt switching entailed in the foregoing is unusualin that a single door-actuated plunger must be capable of simplyshifting electrical excitation from warning to stop lights during amovement in one direction associated with the opening of the door, and,during its movement in the opposite direction, associated with closingof the door, it must momentarily break another circuit which isnevertheless not'interrupted by the other movement.

SUMMARY OF THE INVENTION By way ofa summary statement concerning onepractice of this invention, a school-bus signalling system, involvingsets of different-color warning-and stop-lights which are to be flashedin sequence as the bus is stopped and its door opened to permit boardingor discharge of passengers, includes a conventional motordriven flasherswitch in association with an operatoractuated self-holding solenoidswitch and a single triple-circuit door-actuated switch. When the usualstop is about to be made for passengers, the operator actuated the relayswitch, and the latter energizes itself to sustained closure through thethen-closed contacts of a momentary-interrupt relay circuit of the doorswitch of the thenclosed door. At the same time, the operator-actuatedrelay switch connects electrical excitation to the motor-driven flasher,and the latter commences periodic pulsing of current to alternate onesof amber warningsignal lamps, through different closed lampcircuitcontacts of the door switch associated with the then-closed door. Oncethe door is opened upon stopping of the vehicle, the plunger-armature ofthe door switch is spring-biased to a new position at which it opens thepreviously-closed lamp-circuit contacts associated with the amberwarning lights and transfers the contact closures to those associatedwith red stop lights. Importantly, the momentary-interrupt relay circuitcontacts of the door switch have remained closed, and the stop lightsare thus flashed so long as the door is open. Upon closure of the door,the door-switch plunger is moved back to its initial position, and, inthe course of that particular motion only, the doorswitch contactsassociated with the momentary-interrupt relay circuit are transientlyseparated and the holding coil of the relay switch becomestie-energized. As a result, the

relay switch cuts off all power to the warning system,

In achieving the desired momentary interruption of one set of contactsof the door-responsive switch only during an inward plunger travelassociated with closing of the door, the plunger is shaped to exhibit ashoulder just smaller than the surrounding mated opening through a plateof a contact carrier which cooperates with those particular contacts.Further, a stretchable O-ring is disposed around the plunger, its innerdiameter being less than the outer diameter of the shoulder, and itsmiddle diameter being greater than the diameter of the plate opening. Inits outwardly-extended position, the plunger traps the O-ring betweenits shoulder and the plate, and, as the plunger is moved inwardly duringa door-closing movement, the O-ring necessarily pushes the plateinwardly and separates its shorting contact from the stationary contactsof the interrupt circuit under consideration. That separation is onlymomentary, however, because continued inward travel of the plungercauses the contact plate to strike mechanical stops and the plungershoulder is then forced to push its way through the O-ring. At thattime, the O- ring stretches annularly and rides over the plungershoulder, whereupon the contact-carrier plate then becomes freed ofplunger restraint and is quickly springactuated back to its intitialposition where it again closes with the stationary contacts. When theplunger is later extended outwardly once more, during a dooropeningcycle of its movements, the O-ring is rolled back over the plungershoulder, the latter having a gradual taper promoting that action, andinto a readied position between the shoulder and plate once again; thereis no interruption of contact connections during the last-describedmovement of the plunger, because the contact-carrier plate is notdisturbed by the rollback interaction between the plunger shoulder andO- ring.

Accordingly, it is one of the objects of the present invention toprovide novel and improved vehicle warning-signal switching apparatus oflow-cost and uncomplicated construction which responds to operatoractuation by automatically imposing a sequencing of light flashingsuntil a vehicle door has been both opened and reclosed.

Another object is to provide unique and advantageous switching forschool-bus light-flashing wherein a prescribed sequencing of warning-andstop-light connections is assured by the cooperative relationships of anoperator-actuated self-holding switch and a dooractuated switch whichdevelops a momentary interrupt only during a door-closing operation.

A yet further object is to provide a plunger-operated switch wherein anexpandable O-ring, an aperturcd contact-carrying plate, and a shapedshoulder on the plunger cooperate to produce a transient separation ofcertain switching contacts only during travel of the plunger in one ofits two directions of reciprocal motion.

BRIEF DESCRIPTION OF THE DRAWINGS Although the features of thisinvention which are considered to be novel are expressed in the appendedclaims, further details as to preferred embodiments, as well as tofurther objects and advantages, may be most readily comprehended throughreference to the following description taken in connection with theaccompanying drawings, wherein:

FIG. 1 illustrates an improved SChOOI-bUS lightflashing switchingarrangement, in partly schematic and pictorial conventions;

FIG. 2 is a partly erosssectioned plan view ofa plungeractuatedmultiple-circuit switch, useful in the arrangement of FIG. 1, whichincludes unique momentary-interrupt provisions for one of its circuits;

FIG. 3 provides a sectioned side view of the switch of FIG. 2;

FIG. 4 is plan view like that of FIG. 1, with the switch plunger shownfully depressed;

FIG. 5 represents a sectioned side view of the switch of FIG. 4;

FIG. 6 provides a detail enlargement of a portion of the switch of FIGS.2-5, in a sectioned side view; and

FIG. 7 depicts a self-holding operator-actuated solenoid switch usefulin the arrangement of FIG. 1, with portions broken away and sectioned toexpose constructional details.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings,wherein like reference characters are used for corresponding partsthroughout the several views, the improved switching arrangement isrepresented in association with school-bus warning and stop lights, inFIG. 1. There, an upper rear portion 8 of a school bus is shown toinclude the customary pairs of amber warning lights, 9,, and 9,,, andred stop lights, 10,, and 10,,, and a further stop light 11 for a sidewarning flag is also depicted. Both the pairs of warning and stop lightsare intended to be flashed alternately, and respectively in successionfirst as the vehicle decelerates toward a stop for boarding ordischarging passengers and then as a door is opened. For these purposes,a conventional motorized flasher, 12, including a battery-powered motor12,, and commutator-type switch 12,,, is employed to distribute power tothe warning and stop lights, and the arrangement further includes anoperatoractuated self-holding relay switch 13, and a multiple-circuitdoor-actuated switch 14. When a side warning flag is used, a furthersingle-pole singlethrow momentary switch 15 serves to make an electricalconnection to a vacuum relay.

As the operator approaches a stop for the boarding or discharge ofpassengers, the shaft 13,, of switch 13 is depressed, therebyestablishing electrical continuity between the positive supply of thevehicle battery 16 and an output switch terminal 13,,. From the latterconnection, excitation is delivered to terminal 12,. of the flashercombination 12, causing motor 12,, to rotate and commutate the batterypower alternately to flasher terminals 12,, and 12,. At the same timeswitch shaft 13,, is depressed against internal spring biasing, aninternal self-holding coil within it, 13,. in FIG. 7, becomes energizedby way of its connections with output terminal 13,, and a furtherterminal, 13,,, which is grounded through lead 17 and thenormally-closed momentaryinterrupt pair of switch contacts 14,, and 14,,of door switch 14, the contact 14,, being grounded. Coil 13,. therebymaintains the shaft 13,, in the depressed condition wherein itsassociated contacts establish continuity of electrical supply to theflasher combination 12. Because of this arrangement, even a transientinterruption of the connection between normally-closed doorswitchcontacts 14,, and 14,, will cause the self-holding relay 13 to springopen and cease excitation of the flasher and lights until shaft 13,, isonce again depressed by the operator.

In the aforementioned sequencing wherein the operator has initiallyactuated relay shaft 13,, and thereby started the motor-flashercommutation, the flasher terminals 12,, and 12,. alternately excite theamber warning-signal lights 9,, and 9,, through leads 18 and 19, switchcontacts 14,. and 14,,, switch contacts 14,, and 14,, and leads 20 and21. The necessary individual closures between contacts 14,. and 14,,,and between 14,, and 14,, are established by shorting contact barscarried at the inner end of plunger 14,, of that switch, when it isfully depressed by closure of a vehicle main door. Subsequently, openingof the door, after the bus has stopped, allows the plunger 14,, to besprung to an outwardly-extended position, and the shorting contacts thenalso move forward and thereby establish new connections between contact14,. and 14,, and between 14,, and 14,. Leads 22 and 23, joined with thepair of contacts 14,, and 14,, respectively, then convey the excitationsfrom commutation terminals 12,, and 12,. to the red stop lights 10,, and10,,, such that they flash in alternation so long as the bus remainsstopped with its main door open.

Importantly, all of the signalling is to be terminated only uponreclosureof the door, subject to wholly automatic recycling only if theoperator once'again intentionally depresses plunger 13,, of theself-holding switch 13. In that connection, the continuity betweencontacts 14,, and 14,, of door-switch 14 becomes critical, inasmuch asdepression of the plunger 14,, by a closing door must at leastmomentarily interrupt that continuity while, in subsequent returnmovement of that plunger upon opening of the door, there must be no suchinterruption. A preferred construction of a suitable multicircuitswitch, operated by the door, and including unique provisions for theaforesaid one-way momentary interruption of one of the circuits, appearsin FIG. 2-6.

In certain instances when the same vehicle is to be stopped and the maindoor opened for reasons other than permitting passengers to enter orleave, the abovedescribed sequencing of light flashings must be avoided.The operator then need only omit actuation of the relay switch 13, andonly the usual brake-operated stop lights will then respond. Stops atrailroad crossings, as required by law, can therefore be made withoutviolating statutes prohibiting the flashings of amber and red lightsexcept in connection with school-bus stops serving passengers,

As is represented in FIGS. 1-6, the door-operated switch 14 includes agenerally rectangular form of metal housing, 25, capped by an insulatingcover, 25,,, from which the terminals for switch contacts 14,,-14, and14, and 14, extend outwardly for purposes of connection in the switchingcircuits which have been described. Door-actuated plunger 14,, is urgedtoward its outwardly-extended condition, shown in FIGS. 2 and 3, by acoiled spring 26 trapped between that plunger and its surroundingguide-bushing 27 mounted at the front end of the switch. The innermostend of plunger 14,, is secured to a longitudinally-slidable saddle 28 onwhich two side-by-side contact bars. 29 and 30, of conductive materialare supported in insulated relationship by a contact carrier member 31.When the switch plunger is fully extended (FIGS. 2, 3 and 6), as allowedby an open-door condition, the attached saddle 28 is likewise in aforward position, where the contact bars 29 and 30 respectively engagethe left set of contacts 14,. and 14,, and the right set of contacts14,, and 14,. Full depression of plunger 14,,, upon closure of the doorwith which the switch is associated, causes the saddle 28 to slide to arearmost position (FIGS. 4 and 5) at which the contact bars 29 and 30respectively engage the left set of contacts 14, and 14, and the rightset of contacts 14,, and 14,. Carrier member 31 is biased upwardly, byaction of entrapped spring 32, such that good electrical contacting canbe realized while at the same time allowing the contact bars to be slidbetween the forward and rear switching positions. Locations of theaforesaid sets of top-mounted contacts are designated by dashed lineworkand related reference characters having distinguishing single-primeaccents in FIGS. 2 and 4, where cover 25,, is removed to expose internalfeatures of construction.

A further saddle, 33, is disposed within the housing 25, between saddle28 and the front end of the housing, and supports an insulating carrier34 for a transverselyextending contact bar 35 associated with thecontact pair 14,,-14,,. Unlike saddle 28, the further saddle 33 is notfixed with plunger 14,,, but is instead slidable in relation to itbecause of a slight enlargement of the openings through that saddle 33in relation to external diametric dimensions of the internally-matedplunger. Springs such as springs 36 urge the contact carrier 34 andcontact bar 35 upwardly, for engagement with the contact pair 14,,-14,,,and spring 37 between saddles 28 and 33 tends to maintain saddle 33 inthe illustrated forward position where its contact bar 35 connects thecontact pair 14,,14,,. For purposes of clarity in FIGS. 2 and 4, thecontact bar 35, shown partly broken away, and the saddle 31 with itscontact carrier and contact bars, are superimposed in full-line viewover what would otherwise be cross-sectional parts of the switch.Normally, spring 37 between the two saddles tends to hold saddle 33 inthe forward position irrespective of whether door-actuated plunger 14,,is in the fullyextended position (FIGS. 2 and 3) or fully-depressedposition (FIGS. 4 and 5). And, once the plunger has been fully depressed(FIGS. 4 and 5), it may thereafter extend itself fully outwardly (FIGS.2 and 3), upon opening of the associated door, without interference withthe saddle 33 then in its forward position, because the accommodatingfront and rear saddle openings 36,, and 36,, (FIG. 6) through which theplunger passes are both of larger diameter than any mating parts of thatplunger. However, as the plunger is gradually depressed from the forwardposition (FIGS. 2 and 3) toward the fully-depressed position (FIGS. 4and 5), the saddle 33 is first pressed and moved rearwardly, along withthe plunger, because of an interference which exists between it andanelastically-expandable O-ring 38 and a shaped enlargement 14, on areduceddiameter portion 14,,. of the plunger.

The rear annular face of enlargement 14,- is substantially transverse tothe axis of plunger 14,,. or may be only slightly inclined, whereas itsforward surface (to the left in FIGS. 2-6) is preferably more tapered orfrustro-eonical. O-ring 38 has an inner diameter, in place aboutreduced-diameter plunger portion 14,-. which is about the same as saidreduced diameter. and has an outer diameter in excess of the diameter ofthe front opening 36,, through saddle 33. Further, the radial thicknessof enlargement 14,- is preferably less than one-half the annularthickness of O-ring 38, and the diameter of saddle openings 36,, ispreferably less than that of the circular middle of the O-ring in itsposition around reduced portion 14,. The latter relationships tend, toprevent jamming of the O-ring between the plunger enlargement andsaddle, well as to prevent the O-ring from being squeezed through thesaddle opening 36 A bushing 39, provides a front stop against which theO-ring may rest at times when it is in a stationary dwell condition.

.In line with what has been mentioned hereinabove, rearward movement ofplunger 14,, upon closing of the associated door, causes enlargement 14,to press against O-ring 38, and the latter in turn presses against thefront of saddle 33, such that the entire saddle 33 is forced rearwardlyand its contact bar 35 thus momentarily separates itself from andinterrupts continuity between 3circuit contacts 14,, and 14,. Thatinterruption continues only until the rear of saddle 33 engagesmechanical stops-in its rearward travel, such stops being shown in theform of shallow punched-metal tabs 40 projecting inwardly from the sidesof the housing 25 (FIGS. 2, 4 and 5). These tabs are disposed far enoughrearwardly of the forward position of saddle 33 to permit the latter tomove rearwardly without obstruction until the contact bar 35 ispositively disengaged from the associated contacts 14,, and 14, atypical rearmost orientation .of the rear of saddle 33 being shown indashed linework 33 in FIGS. 4 and 5. Once these stop tabs are engaged bysaddle 33, and rearward movement of the latter is halted, the continuingrearward thrust of the rear face of plunger enlargement 14,- against theinner portions of O-ring 38 cause the latter to be expandeddiametrically and to ride forward over that enlargement. That ride-upexpanding action is illustrated in its initial stage for O-ring 38 inFIG. 6, although it will of course be understood that the plunger andsaddle would in fact be displaced more rearwardly (i.e., to the right)than actually shown in that enlargement which was aimed at clarificationof constructional details. Radiallyoutward squeezing of the inner part,and consequent diametric expansion, of the O-ring 38, followsnecessarily from the facts that is cannot pass through saddle opening 36and that all squeezing is confined to the radially inner portions of theO-ring. Once the O-ring has been expanded in this fashion it ceasesinterfering with plunger movement and rolls forward over thefrusto-conical front surface of enlarge ment 14,, allowing the plungerto advance to its rearmost position (FIGS. 4 and 5) and allowing thespring 37 to snap the saddle 33 forward to the position at which itscontact bar 35 once again engages contacts 14,,and 14 as desired. Duringreturn of the plunger to a fully-extended position (FIGS. 2, 3 and 6) asthe door is opened, the O-ring rests against bushing 39 while thefrustoconical front of enlargement 14, is pulled through it by action ofthe plunger return spring 26, with the result that the O-ring expands,rides over the enlargement 14,, and once again locates itself betweenthe enlargement and saddle 33 in readiness for a subsequentmomentary-interrupt action when the closing door depresses plunger 14,,

Self-holding relay switch 13 may be of the general type illustrated inFIG. 7, and including a solenoid coil 13,. which holds the armature end13,. of its plunger 13,, in a rear fully-depressed position once theplunger 13,, has been depressed by the operator and until the connectionbetween the aforementioned switch contacts 14,, and 14,, has beenmomentarily interrupted during closure of a door. A plunger-returnspring, not shown, then re-extends the plunger 13,, to ready it for asubsequent actuation by the operator. Forthe purposes which have beendescribed hereinabove, the solenoid winding 13 is electrically connectedbetween terminal 13,, and an internal side contact, opposite contact13,, to which the positive side of battery source 16 also becomesconnected whenever contact 13, is shorted with said contact (served byterminal 13) upon bridging of the two by a suitable armature contact13,, movable with the plunger 13,,.

The warning system may include a momentaryinterrupt switch which isseparate from a noninterrupting switch serving the flashing lights,inasmuch as it is not essential that all three circuits be controlled byone switch unit, although that is distinctly advantageous. In othermodifications, the momentary interrupt may instead be changed to becomea momentary connection, and the switch may be associated with actuationsother than by a door. Although an O-ring has been specifically referredto, that element may be fashioned of material other than a rubber, andmay have a cross-sectional configuration other than of the usualcircular form; a split metal or plastic ring, expandable in response tothe applied forces, may be substituted, for example.

Accordingly, modifications, substitutions and variations in relation tothe specific embodiments selected for illustration and description willbe evident to those skilled in the art, and it is therefore to beunderstood that these may be effected without departure from the spiritand scope of this invention in its broader aspects and as set forth inthe appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. Switching apparatus for controlling warning signals such as flashinglights on school buses and the like,

comprising a first operator-actuated switch including an electromagnetwinding and a cooperating armature movable to close a first set ofcontacts in response to operator actuation thereof and maintainingclosure of said contacts only so long as said winding is energized, asecond switch including a second set of contacts and an armature forclosing and opening said second set of contacts in response to movementsof said armature in alternate directions, said second switch includingmeans for changing the continuity condition of said second set ofcontacts between electrically closed and opened conditions transientlyonly during travel of said armature in one of said directions, means formoving said armature in said alternate directions in response tomovements of a part of a vehicle such as a door or the like,warning-signal means, means energizing said warning-signal means from asource through said first set of contacts, and means responsive to thecontinuity condition between said second set of contacts for energizingsaid winding from said source and through said first set of contacts,whereby actuation of said first switch results in excitation of saidwarning signal means until said first switch is automatically openedupon occurrence of movement of said armature of said second switch inboth of its alternate directions of movement.

2. Switching apparatus as set forth in claim 1 wherein saidwarning-signal means comprises lights periodically energized from saidsource through an electricallyoperated flasher switch, both said lightsand said flasher switch being energized from said source through saidfirst set of contacts, and wherein said armature of said second switchincludes a spring-biased plunger extended and depressed in response toopening and closing of a vehicle door.

3. Switching apparatus as set forth in claim 2 wherein said lightsinclude amber warning lights and red stop lights aboard a school bus.wherein said second switch includes a third set of contacts certain ofwhich are associated exclusively with said warning lights and said stoplights, respectively, and contacting means fixed to and movable withsaid plunger between a first position wherein it establishes continuitybetween said flasher switch and the contacts associated with saidwarning lights when said door is closed and a second position wherein itestablishes continuity between said flasher switch and contactsassociated with said stop lights when said door is opened.

4. Switching apparatus as set forth in claim 3 wherein said means forchanging the continuity condition of said second set of contacts onlyduring travel of said armature in one of said directions electricallyopens said second set of contacts during depression of said plunger uponclosing of said door of a school bus.

5. Switching apparatus as set forth in claim 4 wherein said means forchanging said continuity condition of said second set of contactscomprises a contact carrier slidable in axial directions in relation tosaid plunger, a switch housing within which said contact carrier isguided for sliding movement, said plunger being freely mated with saidcontact carrier within said housing by way of an opening through saidcarrier and having a door-actuated end projecting from said housing,spring means urging said plunger end to a forward outwardlyextendingrelationship with a front of said housing, said plunger having anenlargement along one portion thereof between adjoining portions oflesser crosssection, an expandable ring member coaxial with said plungerand having an inner periphery smaller than the outer periphery of saidenlargement and smaller than said opening and having an outer peripherylarger than the outer periphery of said enlargement and larger than saidopening, said enlargement having a periphery smaller than said opening,both the periphery of said enlargement and the opening extendingradially to positions which correspond to less than half the distancefrom the inner to outer peripheries of said ring member, said ringmember being disposed between said carrier and a front part of saidhousing, said enlargement being movable axially with said plunger from aforward position ahead of said front part and ring member to a morerearward position, stop means limiting rearward sliding motion of saidcarrier in relation to said housing beyond a predetermined limitedamount, said second set of contacts comprising a pair of contactsdisposed for electrical closure by said carrier when said carrier is ina forward position and for electrical opening when said carrier is in arearward position within said housing, and spring means urging saidcontact carrier in a forward direction within said housing.

6. Switching apparatus as set forth in claim 5 wherein said ring membercomprises an expandable O-ring of elasticallydeformable material,wherein said opening, said enlargement, and said portions of lessercrosssection are substantially circular, and wherein said enlargementhas a substantially blunt rear surface and a gradually-tapered frontsurface.

7. Switching apparatus for controlling warning signals comprising,

warning signal means responsive to energization with electrical energyfor providing a warning signal, first manually actuated switching meansfor delivering electrical energy to said warning signal means when inthe closed condition having holding means responsive to holding energyfor staying in the closed condition and to interruption of said holdingenergy for returning said first switching means to the open conditionand being responsive to manual actuation for assuming said closedcondition, a source of said holding energy, second switching meanshaving an armature movable in first and second opposed directionsincluding means responsive to movement of said armature in said firstdirection for coupling said holding energy to said holding means andmeans responsive to movement of said armature in said second directionfor interrupting the coupling of said holding energy to said holdingmeans to thereby restore said first switching means to said opencondition.

=l i= l l

1. Switching apparatus for controlling warning signals such as flashinglights on school buses and the like, comprising a firstoperator-actuated switch including an electromagnet winding and acooperating armature movable to close a first set of contacts inresponse to operator actuation thereof and maintaining closure of saidcontacts only so long as said winding is energized, a second switchincluding a second set of contacts and an armature for closing andopening said second set of contacts in response to movements of saidarmature in alternate directions, said second switch including means forchanging the continuity condition of said second set of contacts betweenelectrically closed and opened conditions transiently only during travelof said armature in one of said directions, means for moving saidarmature in said alternate directions in response to movements of a partof a vehicle such as a door or the like, warning-signal means, meansenergizing said warning-signal means from a source through said firstset of contacts, and means responsive to the continuity conditionbetween said second set of contacts for energizing said winding fromsaid source and through said first set of contacts, whereby actuation ofsaid first switch results in excitation of said warning signal meansuntil said first switch is automatically opened upon occurrence ofmovement of said armature of said second switch in both of its alternatedirections of movement.
 2. Switching apparatus as set forth in claim 1wherein said warning-signal means comprises lights periodicallyenergized from said source through an electrically-operated flasherswitch, both said lights and said flasher switch being energized fromsaid source through said first set of contacts, and wherein saidarmature of said second switch includes a spring-biased plunger extendedand depressed in response to opening and closing of a vehicle door. 3.Switching apparatus as set forth in claim 2 wherein said lights includeamber warning lights and red stop lights aboard a school bus, whereinsaid second switch includes a third set of contacts certain of which areassociated exclusively with said warning lights and said stop lights,respectively, and contacting means fixed to and movable with saidplunger between a first position wherein it establishes continuitybetween said flasher switch and the contacts associated with saidwarning lights when said door is closed and a second position wherein itestablishes continuity between said flasher switch and contactsassociated with said stop lights when said door is opened.
 4. Switchingapparatus as set forth in claim 3 wherein said means for changing thecontinuity condition of said second set of contacts only during travelof said armature in one of said directions electrically opens saidsecond set of contacts during depression of said plunger upon closing ofsaid door of a school bus.
 5. Switching apparatus as set forth in claim4 wherein said means for changing said continuity condition of saidsecond set of contacts comprises a contact carrier slidable in axialdirections in relation to said plunger, a switch housing within whichsaid contact carrier is guided for sliding movement, said plunger beingfreely mated with said contact carrier within said housing by way of anopening through said carrier and having a door-actuated end projectingfrom said housing, spring means urging said plunger end to a forwardoutwardly-extending relationship with a front of said housing, saidplunger having an enlargement along one portion thereof betweenadjoining portions of lesser cross-section, an expandable ring membercoaxial with said plunger and having an inner periphery smaller than theouter periphery of said enlargement and smaller thAn said opening andhaving an outer periphery larger than the outer periphery of saidenlargement and larger than said opening, said enlargement having aperiphery smaller than said opening, both the periphery of saidenlargement and the opening extending radially to positions whichcorrespond to less than half the distance from the inner to outerperipheries of said ring member, said ring member being disposed betweensaid carrier and a front part of said housing, said enlargement beingmovable axially with said plunger from a forward position ahead of saidfront part and ring member to a more rearward position, stop meanslimiting rearward sliding motion of said carrier in relation to saidhousing beyond a predetermined limited amount, said second set ofcontacts comprising a pair of contacts disposed for electrical closureby said carrier when said carrier is in a forward position and forelectrical opening when said carrier is in a rearward position withinsaid housing, and spring means urging said contact carrier in a forwarddirection within said housing.
 6. Switching apparatus as set forth inclaim 5 wherein said ring member comprises an expandable O-ring ofelasticallydeformable material, wherein said opening, said enlargement,and said portions of lesser cross-section are substantially circular,and wherein said enlargement has a substantially blunt rear surface anda gradually-tapered front surface.
 7. Switching apparatus forcontrolling warning signals comprising, warning signal means responsiveto energization with electrical energy for providing a warning signal,first manually actuated switching means for delivering electrical energyto said warning signal means when in the closed condition having holdingmeans responsive to holding energy for staying in the closed conditionand to interruption of said holding energy for returning said firstswitching means to the open condition and being responsive to manualactuation for assuming said closed condition, a source of said holdingenergy, second switching means having an armature movable in first andsecond opposed directions including means responsive to movement of saidarmature in said first direction for coupling said holding energy tosaid holding means and means responsive to movement of said armature insaid second direction for interrupting the coupling of said holdingenergy to said holding means to thereby restore said first switchingmeans to said open condition.